However, despite making an offer to bring in the highly-rated Germany international early to cement their hopes of a top-four finish and Champions League qualification, the Bundesliga club have rejected Spurs' proposal.

"There is a request from Tottenham. The offer is not acceptable," Schalke general manager Horst Heldt told reporters.

"But the transfer window is still open. Lewis has not become cheaper today."

Holtby played a starring role as Schalke returned to Bundesliga action after the winter break with a 5-4 win over Hannover on Friday.

Speaking after the game, the midfielder was non-committal regarding his future, insisting he was simply concentrating on Schalke currently.

"I will give all for Schalke until the last second," Holtby told reporters.